U.S. patent number 11,331,628 [Application Number 16/643,301] was granted by the patent office on 2022-05-17 for vapor condenser enhanced by membrane evaporation.
This patent grant is currently assigned to DAIS ANALYTIC CORPORATION. The grantee listed for this patent is DAIS ANALYTIC CORPORATION. Invention is credited to Rasool Nasr Isfahani, Brian Johnson.
United States Patent |
11,331,628 |
Johnson , et al. |
May 17, 2022 |
Vapor condenser enhanced by membrane evaporation
Abstract
A membrane evaporative condenser (MEC) includes a repeating
sequence of channels for evaporation and/or condensation are
arranged, each sequence of channels includes a condensation channel
for condensation of a vapor to a liquid, an evaporation channel,
and zero to one hundred evaporation-condensation channels. The
condensation channel has walls of a non-permeable material which
exterior to the condensation channel share the wall with a liquid
evaporative medium (LEM) conduit that contains a LEM. The LEM
conduit includes a moisture transfer membrane (MTM), where the LEM
can evaporate into an evaporation channel or an
evaporation-condensation channel that can amplify the effect of the
heat transfer for additional mass transfer.
Inventors: |
Johnson; Brian (Tampa, FL),
Isfahani; Rasool Nasr (Tampa, FL) |
Applicant: |
Name |
City |
State |
Country |
Type |
DAIS ANALYTIC CORPORATION |
Odessa |
FL |
US |
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Assignee: |
DAIS ANALYTIC CORPORATION
(Odessa, FL)
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Family
ID: |
1000006313619 |
Appl.
No.: |
16/643,301 |
Filed: |
August 29, 2018 |
PCT
Filed: |
August 29, 2018 |
PCT No.: |
PCT/US2018/048501 |
371(c)(1),(2),(4) Date: |
February 28, 2020 |
PCT
Pub. No.: |
WO2019/046397 |
PCT
Pub. Date: |
March 07, 2019 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20200330923 A1 |
Oct 22, 2020 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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62551537 |
Aug 29, 2017 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C02F
1/448 (20130101); B01D 61/362 (20130101); B01D
61/366 (20130101); B01D 2311/106 (20130101); B01D
2311/2642 (20130101); B01D 2313/38 (20130101); B01D
2311/2669 (20130101); B01D 2313/22 (20130101) |
Current International
Class: |
B01D
61/36 (20060101); C02F 1/44 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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102826700 |
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Dec 2012 |
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CN |
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103387308 |
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Nov 2013 |
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CN |
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103732311 |
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Apr 2014 |
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CN |
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106512738 |
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Mar 2017 |
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CN |
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102013220199 |
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Apr 2015 |
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DE |
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2040314 |
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Jul 1995 |
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RU |
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2012/048788 |
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Apr 2012 |
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WO |
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2016/183477 |
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Nov 2016 |
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WO |
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Other References
Zhu Chunjun et al.--GN 102826700 A Machine Translation--Dec. 19,
2012 (Year: 2012). cited by examiner .
Dais--Dais Analytic Ships Largest Order in 14-Year History--2014
(Year: 2014). cited by examiner .
International Search Report and Written Opinion, PCT International
Application No. PCT/US2018/048501, PCT/ISA/210, PCT/ISA/237, dated
Dec. 6, 2018. cited by applicant.
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Primary Examiner: Spies; Bradley R
Attorney, Agent or Firm: Saliwanchik, Lloyd &
Eisenschenk
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a national stave application of International
Application No. PCT/US2018/048501, filed Aug. 29, 2018, which
claims the benefit of U.S. Provisional Application Ser. No.
62/551,537, filed Aug. 29, 2017, the disclosures of which are
incorporated herein by reference in their entirety, including all
figures, tables and drawings.
Claims
We claim:
1. A membrane evaporative condenser (MEC) comprising a repeating
sequence of channels for evaporation and/or condensation, each
sequence of channels comprising: a condensation channel for
condensation of a vapor to a liquid, the condensation channel
comprising: two walls of a non-permeable material where both walls
of the non-permeable material of channels that do not terminate the
repeating sequence of channels is a shared wall with a wall of a
non-permeable material of a LEM conduit for containment of a liquid
evaporative medium (LEM), the LEM conduit comprising: a first wall
of the non-permeable material; and a second wall comprising a
moisture transfer membrane (MTM), the surface of the MTM outside of
the LEM conduit being a site for evaporating the LEM from the LEM
conduit; at least one LEM inlet to the LEM conduit; at least one
vapor inlet for the vapor; and at least one liquid outlet for the
liquid; zero to one hundred evaporation-condensation channels, each
comprising: the LEM conduit; a second wall comprising the
non-permeable material, the second wall being a site for
condensation of the LEM to an LEM condensate that evaporates from
the MTM; at least one LEM inlet and at least one LEM outlet to the
LEM conduit; and at least one LEM condensate outlet; an evaporation
channel, wherein all of the walls that do not terminate the
repeating sequence of channels comprise LEM conduits and a space
between the MTMs of the LEM conduits or a terminal space between
the MTM and a non-permeable wall of a terminal evaporation channel,
and wherein each of the evaporation channels has at least one
working fluid inlet and a wet working fluid outlet; and an
evaporative chiller and dehumidifier comprising an LEM channel
comprising a first MTM and a second MTM, a vacuum evaporation
conduit between the first MTM and a first wall comprising a
non-porous material, and a condensation conduit comprising the
second MTM and a second wall comprising a non-porous material,
wherein the wet working fluid outlet of the evaporation channel is
configured to maintain a vapor pressure of a wet working fluid of
the wet working fluid outlet of the evaporation channel lower than
a vapor pressure of the LEM channel of the evaporative chiller and
dehumidifier.
2. The MEC according to claim 1, wherein the sequence of channels
has zero evaporation-condensation channels, comprising a repeating
sequence of alternating condensation channels and evaporation
channels.
3. The MEC according to claim 1, wherein the sequence of channels
has 1 to 10 evaporation-condensation channels in the sequence of
channels.
4. The MEC according to claim 1, wherein the MTM is a composite
membrane with a solid pervaporation coating, and wherein the LEM is
water.
5. The MEC according to claim 1, wherein the LEM is from one
source.
6. The MEC according to claim 1, wherein the LEM is from a
plurality of sources.
7. The MEC according to claim 1, wherein the LEM is non-potable
water.
8. The MEC according to claim 7, further comprising a filter before
the LEM inlet.
9. The MEC according to claim 1, further comprising a vapor
compression device, wherein the wet working fluid of the wet
working fluid outlet of the evaporation channel is input to the
compression device and the output of the compression device is
delivered to the vapor inlet of the condensation channel.
10. The MEC according to claim 1, wherein the LEM of the
evaporation channel and the LEM of the evaporation-condensation
channel are from different sources.
11. The MEC according to claim 10, further comprising at least one
pump coupled to at least one of the condensation channel, the
evaporation-condensation channel, and the evaporation channel.
12. The MEC according to claim 1, wherein the LEM is water and the
LEM condensate is purified water.
13. A method of preparing an MEC according to claim 1, comprising:
providing a plurality of condensation channels and evaporation
channels in an alternating sequence; connecting the vapor inlets to
at least one conduit for connection to a vapor source; connecting
the LEM inlets to at least one conduit for connection to a LEM
source; connecting the working fluid inlet to at least one conduit
for connection to a working fluid source; providing the evaporative
chiller and dehumidifier; maintaining the vapor pressure of the wet
working fluid of the wet working fluid outlet of the evaporation
channel lower than the vapor pressure of the LEM channel of the
evaporative chiller and dehumidifier; connecting the vacuum
evaporation conduit to a vacuum source; connecting the liquid
outlets to at least one conduit to at least one reservoir,
recycling device, or drain; and optionally, connecting the LEM
outlets to at least one conduit to at least one reservoir,
recycling device, or drain.
14. The method of preparing an MEC according to claim 13, further
comprising: providing a plurality of evaporation-condensation
channels; and connecting the LEM condensate outlets to at least one
conduit to at least one reservoir, recycling device, or drain.
15. The method of preparing an MEC according to claim 14, wherein
the vacuum source is an aspirator connected to a fluid flow within
the MEC.
16. A device comprising the MEC according to claim 1, wherein the
device is: an HVAC; a process condenser; a distillation device; a
crystallization device; a water treatment device; or a fluid
treatment device.
Description
BACKGROUND OF THE INVENTION
Phase change of heat transfer media is used to efficiently move
heat energy. Commonly, a condenser is used to transfer heat from of
a vapor so that it reaches saturation and condenses into a liquid
with the release of heat that is transferred through a
non-permeable surface to a working fluid that transfers the heat to
the ultimate heat sink via a second, separate process. The working
fluid may be a gas, such as ambient air, where the heated fluid
mixes with the atmosphere to effectively dissipate the thermal
input. Although simply affected, the saturation temperature of the
working fluid within the condenser must exceed the dry-bulb
temperature of the working fluid. Because no mass exchange occurs,
the working fluid temperature rises as it absorbs heat. Since the
density and specific heat of air are very low relative to the heat
released by the phase change of a vapor condensing, a large
volumetric flow is needed to keep the temperature rise of the
working fluid from increasing the saturation temperature. The use
of a liquid coolant, typically water, to transfer the heat to a
separate evaporative cooling device, a cooling tower, lowers the
required saturation temperature of the condenser.
When water is evaporating into the cooling air, it need only exceed
the wet-bulb temperature of the cooling air, which much of the
time, is significantly lower than the dry-bulb temperature. A
negative to having a separate cooling tower is that the condenser's
cooling is only sensible; limiting the working fluid's temperature
rise and requiring a high flow rate. Conventional cooling tower
technology imposes strict limits on the concentration of dissolved
solids in the evaporating fluid to avoid formation of scale
deposits. Additionally, a safety issue arises from the release of
small water droplets into the environment, as these droplets can
carry deadly bacteria such as legionella. This obliges careful
maintenance and regular dosing with chlorine or other oxidants,
which imposes liability and a labor workload that typically limits
cooling tower application to larger installations.
Various attempts have been made over the years to combine cooling
tower and condenser components by spraying liquid water onto the
surface of a heat exchanger to allow evaporative cooling of a thin
film of fluid directly covering the heat exchange surface opposed
to the surface where condensation is occurring. Combining
evaporative cooling with vapor condensation allows the benefit of
evaporative cooling in a single component that improves packaging
and eliminates pumping to transfer water. Because the phase change
heat released from the condensing vapor is conducted with a
negligible resistance to the phase change heat absorption of
evaporative cooling, the working fluid's flow rate needs not be
high to cope with a temperature gain as with sensible heat
exchanges.
The total evaporation of working fluid, such as water, tends to
leave scale deposits on the heat exchange surfaces, which decrease
performance severely. When the thickness of and evaporation rate in
the water film cannot be controlled reliably, operators limit the
dissolved solid concentration of the working fluid in the same
manner that conventional cooling tower operators do. The exposed
water being atomized into an ambient air stream is a potential
source of bacteria, just as with cooling towers.
These shortcomings of the state of the art could be addressable by
single components that combine a selective membrane having an
appropriate geometry of flow channels with a support structure that
are secured together without use of additional spacer, where the
complex 3D geometries generate an efficiency increase. To this end,
practical membrane evaporative condensers and their inclusion in
systems for cooling and dehumidification are presented.
BRIEF SUMMARY OF THE INVENTION
Embodiments of the invention are directed to a membrane evaporative
condenser (MEC) where a repeating sequence of channels for
evaporation and/or condensation are arranged, each sequence of
channels includes a condensation channel for condensation of a
vapor to a liquid, an evaporation channel, and zero to one hundred
evaporation-condensation channels. The condensation channel has at
least one vapor inlet and at least one outlet for liquid and/or
vapor and resides between two walls of a non-permeable material,
where all walls of the non-permeable material of condensation
channels that do not terminate the repeating sequence of channels
comprise a wall shared with an adjacent LEM conduit for containment
of a liquid evaporative medium (LEM). The LEM conduit resides
between a first wall of the non-permeable material and a second
wall including a moisture transfer membrane (MTM), whose surface of
the MTM outside of the LEM conduit is a site for evaporating the
LEM from the LEM conduit. The LEM conduit includes one or more LEM
inlets to the LEM conduit. In some embodiments of the invention,
the MEC includes one or more evaporation-condensation channels,
each evaporation-condensation channel is defined by a LEM conduit,
a second wall of the non-permeable material, which provides a site
for condensation of the LEM to an LEM condensate that evaporates
from the MTM, a LEM inlet to the LEM conduit, an LEM outlet to the
LEM conduit, and an outlet for the LEM condensate. The evaporation
channel has all of the walls that do not terminate the repeating
sequence of channels being LEM conduits where the space between the
MTMs of the LEM conduits or a terminal space between the MTM and a
non-permeable wall of a terminal evaporation channel allows
transport of a gaseous working fluid from one or more dry working
fluid inlet to one or more wet working fluid outlet.
According to an embodiment of the invention, the MEC can be a
repeating sequence of alternating condensation channels and
evaporation channels. In another embodiment of the invention, there
can be 1 to 10, or even up to 100 evaporation-condensation channels
situated between a condensation channel and the evaporation channel
in the sequence of channels.
The MTM can be Aqualyte.TM. with the LEM is water. The LEM can be
from one source or a plurality of sources that are the same or
different material. When the LEM is non-potable water the MEC can
function as a water purifier as the LEM condensate can be pure
water. The non-potable water can be filtered to remove solids that
might foul an LEM conduit. The filter can be about 20 microns or
finer. The LEM of the evaporation channel and the LEM of the
evaporation-condensation channel can be from different sources.
In an embodiment of the invention, the MEC can employ a vapor
compression device. For example, the wet working fluid from the
evaporation channel can be the input to the compression device and
the output of the compression device can be delivered to the vapor
inlet of the condensation channel. One or more pumps can be coupled
to at least one of the condensation channel, the
evaporation-condensation channel, and the evaporation channel.
In an embodiment of the invention, the MEC includes at least one
evaporative chiller and dehumidifier, each having an LEM channel
between a first MTM and a second MTM, with a vacuum evaporation
conduit between the first MTM and a first wall of a non-porous
material, and a condensation conduit between the second MTM and a
second wall comprising a non-porous material wherein the wet
working fluid outlet of the evaporation channel is connected to the
condensation conduit.
Embodiments of the invention are directed to a method of preparing
an MEC, as described above. In one embodiment, the method involves
providing a plurality of condensation channels and evaporation
channels in an alternating sequence, connecting the vapor inlets to
at least one conduit for connection to a vapor source, connecting
the LEM inlets to at least one conduit for connection to a LEM
source, connecting the dry working fluid inlet to at least one
conduit for connection to a dry working fluid source, connecting
the liquid outlets to at least one conduit to at least one
reservoir, recycling device, or drain, and, optionally, connecting
the LEM outlets to at least one conduit to at least one reservoir,
recycling device, or drain. In another embodiment of the invention,
the method includes the additional steps of providing a plurality
of evaporation-condensation channels and connecting the LEM
condensate outlets to at least one conduit to at least one
reservoir, recycling device, or drain. In another embodiment of the
invention, the method also includes providing at least one
evaporative chiller and dehumidifier, connecting the wet working
fluid outlet to the condensation conduit, and connecting the vacuum
evaporation conduit to a vacuum source. The vacuum source is an
aspirator connected to a fluid flow within the MEC.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a membrane evaporative condenser (MEC), according to
an embodiment of the invention, with a repeating series of
condensation channels and evaporation channels.
FIG. 2 shows a multiple-effect MEC where a plurality of
evaporation-condensation channels are inserted between each pair of
the condensation channels and evaporation channels, according to an
embodiment of the invention.
FIG. 3 shows a multiple effect MEC where a plurality of
evaporation-condensation channels are inserted between each pair of
the condensation channels and evaporation channels with multiple
sources of liquid evaporative medium (LEM) is used, according to an
embodiment of the invention.
FIG. 4 shows an arrangement of the MEC including fluid inlets and
outlets, according to an embodiment of the invention.
FIG. 5 shows an evaporative chiller and dehumidifier that can be
included in the MEC, according to an embodiment of the
invention.
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the invention are directed to membrane evaporative
condensers (MECs) where a condensing fluid, which can be water or
any other practical condensable fluid, and a working fluid, which
can be water or any other practical evaporative fluid, reside on
opposite sides of a non-permeable heat transfer surface with a thin
layer of the working fluid retained between the non-permeable heat
transfer surface and a selectively permeable mass-transport
membrane. The MEC can be included into any device that rejects
enthalpy from a condensing working fluid that: modifies a
temperature or moisture level of a building or other enclosure,
such as an HVAC application; circulates as part of a process; is
part of a distillation device that isolates one fluid from a
solution or mixture; performs crystallization to concentrate
dissolved solids in solution until precipitation commences; or is
part of a thermal process for treating water or other liquids by
removing nonvolatile compounds. A cross-section of the MEC is
illustrated in FIG. 1.
As illustrated in FIG. 1, two non-permeable heat transfer surface 1
define a channel for transport with gravity of a condensing vapor
3, such as, but not limited to, steam, which enters and progresses
through the channel. The condensing vapor 3 providing heat that is
transferred through the non-permeable heat transfer surfaces 1 of
wall 2 of a heat exchange medium (HEM), which can be the surface of
a metal or other material film displaying a sufficiently high heat
transfer coefficient and any needed resistance to pressure and
corrosion. The condensing vapor undergoes condensation and exits
the channel as a liquid 4. Heat from the condensing vapor is
provided through the wall 2 into a liquid evaporative medium (LEM)
contained in a LEM conduit 6 defined by wall 2 and a permeable
membrane (PM) 5. The LEM can be water or any other liquid fluid
that can evaporate with the heat provided by the condensing vapor.
Vapor passes through the PM 5, which for water can be a moisture
transfer membrane (MTM), and the PM is recited herein as a MTM,
though it is to be understood that the MTM can be a PM for some
chemical other than water and these other LEMs can be used with a
MTM where the "moisture" is a liquid other than water. Where water
and/or steam are recited, the water represents any other
appropriate liquid and the steam represents any appropriate vapor.
The moisture passing through the MTM 5 and evaporates into a gas
stream that comprised a working fluid that enters an evaporation
channel defined between two MTMs 5's as a relatively "dry" gas 7
and exits as a relatively "wet" gas 8. The "dry" gas being one
without vapor from the LEM and the "wet" gas is a vapor comprising
at least some LEM vapor. The dry gas, as used herein, is a gas that
can absorb additional LEM vapor at the working temperature and a
wet gas, as used herein, is a gas from which LEM vapor can condense
at the working temperature. Although the working temperature can be
different in the condensation channel and the evaporation channel
can be of the same temperature. Though as shown, the MEC displays
only two channels for the condensing medium and three channels for
evaporation from the MTM, with the two outside channels for
evaporation defined by one MTM and a containing wall, the MEC,
according to embodiments of the invention, is not so limited can
include multiple repeating pairs of channels for condensation and
evaporation. The outside channels can be independently for
condensation or for evaporation.
The heat provided for evaporation is ultimately provided by the
condensation of the condensing vapor 3 to the liquid 4, for
example, steam condensing to water. The working fluid can be air
and the LEM can be water. The LEM can be in flow, or can be
effectively in a closed channel that remains filled by contact with
an LEM source. A flow to the LEM promotes mixing to maintain a
nearly constant thermal and, when the LEM is a solution a constant
concentration profile, across the thickness of the conduit within
the LEM conduit. The MEC, according to embodiments of the
invention, has a number of advantageous qualities including, but
not limited to: allowing a single component to replace the typical
combination of liquid-cooled condenser and cooling tower currently
used; because the MEC interacts with the working fluid by mass
transfer, the condensing fluid saturation temperature needs only to
exceed the wet-bulb temperature of the working fluid; by
eliminating circulation of the evaporative medium from a condenser
to a separate cooling tower, the MEC eliminates the dependence
between the temperature differentials and mass flow rate of the
evaporative medium; allowing a significant size reduction and the
possibility the total elimination of a circulation pump and its
parasitic power requirements; and to avoid direct evaporation with
the formation of very small airborne droplets or a thin continuous
film of the evaporative medium for effective heat transfer that
occurs without an MTM to mediate the mass transfer of the LEM.
The MECs, according to embodiments of the invention, can be
included in: enhanced HVAC systems, as disclosed in U.S. Pat. No.
8,470,071; fluid treatment systems, as disclosed in U.S. Pat. No.
9,283,518; evaporative chilling systems, as disclosed in PCT
Application No. PCT/US2016/056064; or compact membrane-based heat
and mass exchangers, as disclosed in U.S. patent application Ser.
No. 15/969,449. All of these disclosures are incorporated by
reference herein. By evaporation from a thin channel of an LEM
maintained between a non-permeable material and a permeable
membrane, an efficient transfer of heat from a fluid contacting the
surface of the non-permeable material opposite the channel to a
fluid contacting the surface of the MTM opposite the LEM channel.
Herein, condensable or evaporative fluids are often stated to be
water, air, and steam but, as would be appreciated by one of skill
in the art, other chemical species can provide the same functions
within the devises disclosed in this specification.
In an embodiment of the invention, the channel for condensation and
evaporation can be partitioned into multiple layers as a
multiple-effect configuration MEC, as shown in FIG. 2 for a four
layer configuration. The layers display a redundant series of
condensation channels, for example a steam condensation channel,
where a first channel is a steam condensation channel with entry
for the condensing vapor 13 and exits as condensed liquid 14
centered between two non-permeable HEMs 12s contacting the LEM
conduit 16, each contacting PM 15 on the faces of the HEM 12 that
are distal to the steam condensation channel 13. In this
configuration, the water vapor exiting the MTM 15 that shares a HEM
12 with the steam condensation channel and the water vapor
condenses against an adjacent HEM 12 where the heat released at a
first HEM drives evaporation from the LEM conduit 16 through the
contacting MTM 15 into a secondary evaporation-condensation
channel; where the condensate from the LEM conduit 16 condenses
against a second HEM 12 allowing it to exit as to a secondary
liquid 24. This cascade of condensation and evaporation in
consecutive evaporation-condensation channel transmits the energy
of the steam condensation through each layer of the cascade by
successive evaporations and condensations. The initial energy input
from the steam or other condensing medium is effectively re-used in
the cascade, most effectively when the subsequent
evaporation-condensation channel is at or near saturated in water
or other condensable vapor. The number of subsequent
evaporation-condensation channels can be one to ten or more,
depending on the efficiency of heat transfer and the quality of the
LEM in the LEM conduit 16. This increases the Gained Output Ratio
(GOR) of the process, multiplying the amount of liquid evaporated
for a given amount of thermal input. Ultimately, an n.sup.th
subsequent evaporation-condensation channel has its HEM 12 shared
with one where the LEM conduit 16 and its MTM 15 delivers the
evaporated water or other vaporizable fluid into a gas stream that
comprised a working fluid, such as air, that enters an evaporation
channel defined between two MTMs 15's as a relatively "dry" gas 17
and exits as a relatively "wet" gas 18. The sequence between the
condensation channel, through subsequent evaporation-condensation
channels and the evaporation channel can be repeated a plurality of
times, for example 2 to 100 or more times.
In an embodiment of the invention, the multiple-effect
configuration MEC can be modified so that no working fluid is
introduced as a "dry" gas 17, into the evaporation channel whose
inlet being removed, valved off, or capped; the "wet" gas 18
exiting from the MEC is diverted to a vapor compression device, not
shown, which can be a mechanical, electrochemical, or other form of
compressor, instead of being condensed immediately. A valved inlet
to the evaporation channel can be used to maintain a desired
pressure of the evaporated vapor by removing or adding the vapor as
required or desired to achieve the desired performance. The
high-pressure vapor exiting the compressor is routed as the
condensing vapor 13 to the first condensation channels, replacing
the externally-supplied steam. This allows mechanical energy,
typically supplied by an electric motor, to move heat inside the
system, with the heat of condensation recaptured for evaporation at
a different location. This heat pump effect can make the system
more energy efficient than a thermally powered system.
According to an embodiment of the invention, the multiple-effect
configuration MEC allows the steam condensed liquid 14 and the
condensed liquid 24 provided by evaporation of the LEM to be
combined in a conduit 23 and collected as pure water or other
liquid. In this manner the LEM can be almost any quality of water,
limited only by the amount of suspended solids. Hence, any
non-potable water can be used upon filtration to remove
particulates in excess of about 20 microns in dimension. The
non-potable water used can be recycled through a conduit 21 of the
MEC where unrecycled non-potable water can be added at an inlet 22
as required based on the removal of condensed liquid 24 and removed
at an outlet 25 to maintain the required water portions to maintain
the MEC's proper function.
The multiple-effect MEC, according to embodiments of the invention,
achieve superior performance due to the features provided by the
MTM interface. The MEC provides a reliable predetermined surface
area for evaporation. The MTM ensures a continuous film of
evaporative fluid free of local dry spots from developing and
depositing scale on the surface. The LEM behind the MTM is
pressurized by the column of fluid above it, so a circuit of fluid
recovers the energy spent elevating the fluid to the top of the
device. A conventional device without an MTM cannot sustain this
pressure, requiring the pumping of liquid back to the top of the
column against the elevation change. A distribution manifold within
the LEM layer uses significantly less pressure to spread the flow
evenly across the MTM surface than does spray nozzles used in many
conventional evaporative cooling devices for distribute the
evaporative fluid. Direct contact of the LEM with working fluids,
as in cooling tower application, allows any airborne particles in
the cooling flow to be captured by the working fluid. This disrupts
an even flow of liquid allowing formation of local dry spot and
causes the accumulation of dirty water in the open collection basin
at the base of the tower, which requires frequent maintenance and
result in the health hazard of mold grow.
By using a fouling-resistant membrane, such as a composite membrane
with a solid pervaporation coating facing the evaporation medium,
such as Aqualyte.TM., the LEM can be highly concentrated relative
to a conventional cooling tower. Conventional towers are tending
towards use of highly treated reclaimed water as an alternative to
potable water, which is not required by MTMs, such as Aqualyte.TM.,
which can be operated with wastewater that are solely pretreatment
by screening of solids or with seawater and brines with up to 25%
salinity. The MEC, according to embodiments of the invention, has
the potential to dramatically change the cooling tower market to
use of non-potable water, as power plant evaporative cooling
accounts for approximately 41% of fresh water withdrawals in the
US. By using a selective MTM, the transport of microbes to and from
the LEM eliminates any spreading airborne toxins with all
contaminants and toxins remaining submerged in the LEM. The
interface between the LEM at the MTM assures transfer and
evaporation occurs at the molecular level, so no formation of
droplets of water that can sustain and transmit microbial
populations occurs that can be entrained in the working fluid.
FIG. 3 shows incorporation of a multiple-effect MEC, according to
embodiments of the invention, into a flat plate heat-and-mass
exchanger that incorporates multiple stages of evaporation and
condensation into a single component and uses a plurality of LEM
sources. In the configuration shown, a pattern of layers of MTM and
non-permeable HEMs mediate between different fluid streams. As
illustrated in FIG. 3: steam 33 is generated by an external heat
source, such as boiler 46, where it condenses in a condensation
channel between a pair of HEM 32, generating liquid condensate 34
that can be returned to the boiler in a closed loop via a pump 39
or removed from the system. The heat from this steam condensation
within a condensation channel is transferred thought the HEM 32
into an LEM conduit 36 within an evaporation-condensation channel.
This heated LEM is process water preheated in a heat exchanger 47
using warm condensate liquid 34 to provide the sensible heat. The
process LEM is transmitted via pump 48 into the channel defined by
the HEM 32 and the MTM 35. Vapor passes from the MTM 35 contacting
the LEM conduit 36 into the evaporation-condensation channel where
it condenses into a second liquid 44 on an adjacent second HEM 42
at a lower temperature than the liquid condensate 34. That
condensation to second liquid 44 at HEM 42 causes evaporation from
a second LEM conduit 46. The concentrated LEM is combined with a
source of LEM 50 and delivered via pump 49 in a recycling loop,
where the LEM passes through the MTM 45 into an evaporation channel
of the MEC where the "dry" gas 37 draws the vapor from the MTM 45
and exhausts it as "wet" gas 38.
According to an embodiment off the invention, FIG. 4 shows a
cross-section of an exemplary, non-limiting configuration of a flat
plate heat-and-mass exchanger that can accommodate the equivalent
MEC to that shown in FIG. 3. Two separate subcomponents facilitate
the implementation of the MECs. The first subcomponent is an "air
slat" 51 that separates and supports adjacent MTMs to provide a
space for air to flow in 57 and out 58 of the evaporation channels
while sealed from the steam 53 its condensate 54 inlets and outlets
and inlets 55 and outlets 56 for water or other LEM 55 passing in
and out of internal steam condensation channels and
evaporation-condensation channels. The second sub-component is a
"steam slat" 52 with a complementary arrangement to the air slat
but is vacuum sealed and comprises a suitable non-permeable heat
transfer material to distribute steam between adjacent pairs of
HEMs where the steam condenses in the MECs and seal the steam
channels from the evaporation-condensation channels. The air slats
and steam slats alternated in a stacked arrangement with seals
between the compartments that permits the interstitial space to be
filled with the water or other evaporative medium.
In many air conditioning applications, a stream of moist warm air
68 is chilled and dehumidified to cool dry air 67. In an embodiment
of the invention, an evaporative chiller and dehumidifier comprises
an LEM that is water can be confined between a pair of MTMs 62, as
shown in FIG. 5. On the opposite side of the first MTM, a vacuum
evaporation conduit can be formed between a non-permeable barrier
72 and the first MTM 62. The MTM 62 allows water molecules to pass
from the water LEM channel 66 into the vacuum to provide a water
vapor 70 with evaporation, which causes cooling. The magnitude of
the applied vacuum 69 controls the water temperature in the water
of the LEM channel 66. Simultaneously, a stream of moist air 68 is
introduced in a condensation conduit defined by the second MTM 62
on the opposite side of the LEM channel 66 and a second
non-permeable barrier 62. The chilled water channel acts as
desiccate drawing water molecules from the air stream to dehumidify
the moist air 68 to cool dry air 67. The warm air 68 and the cool
water LEM channel 66 exchange sensible heat to reduce the air
stream's temperature. This evaporative chiller and dehumidifier can
be coupled with the MECs, according to embodiments of the
invention, or may be used alone or in conjunctions with other air
conditioning devices. For example, the moist exhaust air of the
multiple effect MEC can be passed across the LEM channel 66
transferring its humidity and some heat to the vacuum. The vacuum
source can be a mechanical vacuum pump, a diffusion pump, or an
aspirator, such as a water aspirator. When the vacuum source is an
aspirator, the water or other fluid source to the aspirator can be
provided by a flow in the MEC, for example, by the LEM condensate
flow, the LEM outlet flow, the liquid outlet of the condensation
channel, any water flow to any LEM inlet, or the fluid source can
be extra to the MEC.
All patents and patent applications referred to or cited herein,
supra or infra, are incorporated by reference in their entirety,
including all figures and tables, to the extent they are not
inconsistent with the explicit teachings of this specification.
It should be understood that the examples and embodiments described
herein are for illustrative purposes only and that various
modifications or changes in light thereof will be suggested to
persons skilled in the art and are to be included within the spirit
and purview of this application.
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